This is very neat. I’m trying to figure out if you can embed the flow chart builder itself into a post/site. I can imagine for some more complex topics, people would like to be able to move things around/play with the design.
I believe it would be tractable to allow for an additional export option (i.e. Cytoscape.js JSON, CSS) in Flowchart.fun so you could load your figure into a Cytoscape.js instance in your site. This approach would allow for interactive features in your site (e.g. click a node to go to the corresponding section in your article).
If you're looking for something more along the lines of an embedded tweet, it may be possible to use the fullscreen export link in an iframe.
Perhaps Rob could chime in with more details. I'm not involved with Flowchart.fun, but I am a fan. Congratulations on shipping your latest release, Rob.